Abstract:

A variable cutoff web printing press is provided including a first plate
cylinder for printing a first color of first and second images and a
second plate cylinder for printing a second color of the first and the
second images. The printing press also includes a common blanket
cylinder. The first and second plate cylinders contact the common blanket
cylinder and transfer the first and second images to the common blanket
cylinder. The printing press also includes a first transfer body for
receiving the first image from the common blanket cylinder and
transferring the first image to a web and a second transfer body for
receiving the second image from the common blanket cylinder and
transferring the second image to the web. A method of variable cutoff web
printing is also provided.

Claims:

1. A variable cutoff web printing press comprising:a first plate cylinder
for printing a first color of first and second images;a second plate
cylinder for printing a second color of the first and the second images;a
common blanket cylinder, the first and second plate cylinders contacting
the common blanket cylinder and transferring the first and second images
to the common blanket cylinder;a first transfer body for receiving the
first image from the common blanket cylinder and transferring the first
image to a web; anda second transfer body for receiving the second image
from the common blanket cylinder and transferring the second image to the
web.

2. The variable cutoff web printing press recited in claim 1 wherein the
first transfer body includes a first circumferential section movable with
respect to a second circumferential section and the second transfer body
includes a third circumferential section movable with respect to a fourth
circumferential section.

3. The variable cutoff web printing press recited in claim 2 wherein the
first transfer body includes a first supporting cylinder supporting the
first and second circumferential sections and the second transfer body
includes a second support cylinder supporting the third and fourth
circumferential sections.

4. The variable cutoff web printing press as recited in claim 1 further
comprising a third plate cylinder for printing a third color of the first
and the second images on the common blanket cylinder.

5. The variable cutoff web printing press as recited in claim 4 further
comprising a fourth plate cylinder for printing a fourth color of the
first and the second images on the common blanket cylinder, the first,
second, third and fourth plate cylinders acting together to print first
and second four color images on the common blanket cylinder, the common
blanket cylinder transferring the first four color image to the first
transfer body and the second four color image to the second transfer
body.

6. The variable cutoff web printing press as recited in claim 1 wherein
the first plate cylinder includes at least one first plate carrying the
first color of the first image and the first color of the second image
and the second plate cylinder includes at least one second plate carrying
the second color of the first image and the second color of the second
image.

7. The variable cutoff web printing press as recited in claim 6 wherein
the first image and the second image form a continuous image having a
cutoff length, and the at least one first plate can be removed and
replaced with at least one first replacement plate and the at least one
second plate can be removed and replaced with at least one second
replacement plate;wherein the at least one first replacement plate and
the at least one second replacement plate print a first replacement image
and a second replacement image on the common blanket cylinder, the first
replacement image and the second replacement image forming a replacement
continuous image having a replacement cutoff length;wherein the
replacement cutoff length varies from the cutoff length.

8. The variable cutoff web printing press recited in claim 1 further
comprising a first impression cylinder and a second impression cylinder
wherein the first transfer body contacts the first impression cylinder
via the web during the printing mode and the second transfer body
contacts the second impression cylinder via the web during the printing
mode.

9. The variable cutoff web printing press recited in claim 1 wherein the
common blanket cylinder has a circumference that is an integer multiple
of a sum of a circumference of the first plate cylinder and a
circumference of the second plate cylinder.

10. A method of variable cutoff web printing comprising the steps
of:transferring a first first image and a second first image to a common
blanket cylinder;transferring the first first image from the common
blanket cylinder to a first circumferential section movable with respect
to a second circumferential section having a same rotational axis as the
first circumferential section;printing the first first image on a web
using the first circumferential section;transferring the second first
image from the common blanket cylinder to the second circumferential
section; andprinting the second first image on the web using the second
circumferential section.

11. The method of printing as recited in claim 10 wherein the first and
the second first images are four color images.

12. The method of printing as recited in claim 10 further comprising
rotating the first circumferential section at a varying velocity after
the first first image is printed on the web using the first
circumferential section.

13. The method of printing as recited in claim 10 further
comprising:transferring a first second image and a second second image to
the common blanket cylinder;transferring the first second image from the
common blanket cylinder to third circumferential section movable with
respect to a fourth circumferential section having a same rotational axis
as the third circumferential section;printing the first second image on
the web between the first and the second first images using the third
circumferential section;transferring the second second image from the
common blanket cylinder to the fourth circumferential section;
andprinting the second second image on the web following the second first
image using the fourth circumferential section.

Description:

BACKGROUND OF INVENTION

[0001]The present invention relates generally to a printing press and more
specifically to a variable cut off printing apparatus and method.

[0002]U.S. Pat. No. 5,950,536 discloses a variable cutoff offset press
unit wherein a fixed cutoff press is adapted to a variable cutoff press
while maintaining the size of the blanket cylinders. A plate cylinder
sleeve has a variable outer diameter, whereby a length of an image to be
printed is varied proportionally to a variable outer diameter while
maintaining an outer diameter of the gapless blanket cylinder sleeve
constant. The size of a plate cylinder is changed by using a sleeve
mounted over the plate cylinder or adding packing under a plate to
increase the diameter of the plate cylinder.

[0003]U.S. Pat. No. 6,327,975 discloses a method and apparatus for
printing elongate images on a web. A first printing unit prints a first
image portion on the web at prescribed spacings, by moving the impression
cylinder away from the blanket cylinder each time one first image portion
is printed. A second printing unit prints a second image portion on the
spacings left on the web by the first printing unit, also by moving the
impression cylinder away from the blanket cylinder each time one second
image portion is printed. A variable speed motor rotates each blanket
cylinder, while each time the associated impression cylinder is held away
to create a space on the web for causing printing of the first or the
second printing portion at required spacings.

[0004]U.S. Pat. No. 7,066,088 discloses a variable cut-off offset press
system and method of operation which utilizes a continuous image transfer
belt. The offset printing system comprises at least two plate cylinders
adapted to have thereon respective printing sleeves. Each of the printing
sleeves is adapted to receive colored ink from a respective ink source.
The system further comprises at least a impression cylinder, wherein the
image transfer belt is positioned to contact each of the printing sleeves
at respective nips formed between respective ones of the plate cylinders
and the at least one impression cylinder.

BRIEF SUMMARY OF THE INVENTION

[0005]A variable cutoff web printing press is provided including a first
plate cylinder for printing a first color of first and second images and
a second plate cylinder for printing a second color of the first and the
second images. The printing press also includes a common blanket
cylinder. The first and second plate cylinders contact the common blanket
cylinder and transfer the first and second images to the common blanket
cylinder. The printing press also includes a first transfer body for
receiving the first image from the common blanket cylinder and
transferring the first image to a web and a second transfer body for
receiving the second image from the common blanket cylinder and
transferring the second image to the web.

[0006]A method of variable cutoff web printing is also provided. The steps
include transferring a first first image and a second first image to a
common blanket cylinder, transferring the first first image from the
common blanket cylinder to a first circumferential section movable with
respect to a second circumferential section having a same rotational axis
as the first circumferential section, printing the first first image on a
web using the first circumferential section, transferring the second
first image from the common blanket cylinder to the second
circumferential section, and printing the second first image on the web
using the second circumferential section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]The present invention is described below by reference to the
following drawings, in which:

[0008]FIG. 1 shows a schematic side view of a perfecting printing press
according to an embodiment of the present invention;

[0009]FIG. 2A shows a schematic side view of a nonperfecting printing
press according to an embodiment of the present invention;

[0010]FIG. 2b shows a schematic side view of the nonperfecting printing
press shown in FIG. 2A;

[0011]FIG. 2c shows a schematic side view of the nonperfecting printing
press shown in FIGS. 2a and 2b; and

[0013]Variable cutoff printing presses have been developed to allow for
printing products of different sizes on the same printing press without
having to change plate and blanket cylinders. Changing plate and blanket
cylinders to correspond to the cutoff of the image that needs to be
printed can be a time consuming and difficult process. It also may
require purchasing and storing cylinders of multiple sizes.

[0014]FIG. 1 shows a schematic side view of a perfecting printing press 30
according to an embodiment of the present invention. Printing press 30
includes two print units 10 and 20 printing on opposite sides of a
passing web 12. Print unit 10 includes plate cylinders 14, 15, 16, 17,
transfer bodies 135, 136 and common blanket cylinder 18. Transfer bodies
135, 136 include circumferential sections 31, 32, 33, 34 and support
cylinders 35, 36, respectively. In a preferred embodiment plate cylinders
14, 15, 16, 17 may include two printing plates disposed about the surface
of each plate cylinder 14, 15, 16, 17. Each plate cylinder 14, 15, 16, 17
is inked with a different colored ink and each plate cylinder 14, 15, 16,
17 rotates clockwise about a respective axis during a printing mode. The
ink colors may be black, cyan, yellow and magenta, respectively, for
example. Inked images are passed from each plate cylinder 14, 15, 16, 17
to common blanket cylinder 18, which then passes the images to
circumferential blanket sections 31, 32, 33, 34, respectively. In turn,
circumferential blanket sections 31, 32, 33, 34, which are rotating
clockwise about respective support cylinders 35, 36 during the printing
mode, print the images on the web. The images need to be reverse images
so that the double transfer of images, first through common blanket
cylinder 18, then through the respective circumferential blanket sections
31, 32, 33, 34, will be right-reading.

[0015]During the printing mode, plate cylinders 14, 15, 16, 17 act
together to print a first four color image on common blanket cylinder 18.
Each plate cylinder 14, 15, 16, 17 is phased to print an inked image of
one color so that the four different colored images printed respectively
by plate cylinders 14, 15, 16, 17 are aligned to form a first four color
image on common blanket cylinder 18. Plate cylinder 17 rotates and a
first plate on plate cylinder 17 prints an inked image of a first color
on rotating common blanket cylinder 18. When the inked image of the first
color approaches a nip formed between plate cylinder 16 and common
blanket cylinder 18, a first plate on plate cylinder 16 prints an inked
image of a second color on rotating common blanket cylinder 18, directly
overprinting the inked image printed by the first plate of plate cylinder
17. When the overprinted inked images printed by respective first plates
on cylinders 16, 17 approach a nip formed between plate cylinder 15 and
common blanket cylinder 18, a first plate on plate cylinder 15 prints an
inked image of a third color on rotating common blanket cylinder 18,
directly overprinting the respective first images printed by respective
first plates on plate cylinders 16, 17. When the overprinted inked images
printed by respective first plates on plate cylinders 15, 16, 17 approach
a nip formed between plate cylinder 14 and common blanket cylinder 18, a
first plate on plate cylinder 14 prints an inked image of a fourth color
on common blanket cylinder 18, at a position on common blanket cylinder
18 so that the image printed by the first plate on plate cylinder 14
overprints the respective images printed by the first plates on plate
cylinders 15, 16, 17. Thus, the first plate on plate cylinder 14
completes a first four color image on common blanket cylinder 18.

[0016]Common blanket cylinder 18 transfers the first four color image
printed by plate cylinders 14, 15, 16, 17 to one of circumferential
sections 31, 32, depending on the phasing of circumferential sections 31,
32. Whichever circumferential section 31, 32 receives the first four
color image printed by plate cylinders 14, 15, 16, 17 from common blanket
cylinder 18 then prints the first four color image on web 12. Plate
cylinders 14, 15, 16, 17, during operation, should be in constant contact
with common blanket cylinder 18. In a preferred embodiment, the surfaces
of plate cylinders 14, 15, 16, 17 and common blanket cylinder 18 are
traveling at a substantially equal constant velocity.

[0017]After plate cylinders 14, 15, 16, 17 print a first four color image
on common blanket cylinder 18, respective second plates on plate
cylinders 14, 15, 16, 17 print a second four color image on common
blanket cylinder 18. The second four color image should be printed
similar to the first four color image, with second plates on plate
cylinders 14, 15, 16, 17 overprinting in a manner similar to how first
plates of plate cylinders 14, 15, 15, 17 printed the first four color
image.

[0018]The second four color image printed by plate cylinders 14, 15, 16,
17 is then transferred from common blanket cylinder 18 to either
circumferential section 33, 34, depending on the phasing of
circumferential sections 33, 34, which rotate clockwise about support
cylinder 36 during operation. Whichever circumferential section 33, 34
receives the second four color image printed by plate cylinders 14, 15,
16, 17 from common blanket cylinder 18 then prints the second four color
image on web 12.

[0019]Plate cylinders 14, 15, 16, 17, common blanket cylinder 18, and
circumferential sections 31, 32, 33, 34 are appropriately configured and
phased so that circumferential sections 31, 32 print first four color
images on web 12 printed by the respective first plates of plate
cylinders 14, 15, 16, 17 on common blanket cylinder 18 and
circumferential sections 33, 34 print second four color images on web 12
printed by the respective second plates of plate cylinders 14, 15, 16, 17
on common blanket cylinder 18. Circumferential sections 31, 32, 33, 34
are also appropriately configured and phased so that circumferential
sections 31, 32 print every other four color image on web 12, while
circumferential sections 33, 34 print intervening four color images. In a
preferred embodiment, there should not be any unprinted space between the
first four color images printed by circumferential sections 31, 32 and
adjacent second four color images printed by circumferential sections 33,
34.

[0020]Print unit 20 includes plate cylinders 24, 25, 26, 27 and transfer
bodies 145, 146. Transfer bodies 145, 146 may include support cylinders
45, 46 and circumferential sections 41, 42, 43, 44 similar to support
cylinders 35, 36 and circumferential sections 31, 32, 33, 34 of transfer
bodies 135, 136, respectively. Two plates are disposed about the surface
of each plate cylinder 24, 25, 26, 27. Each plate cylinder 24, 25, 26, 27
is inked with a different color ink and rotates counterclockwise about a
respective axis during operation. Plate cylinders 24, 25, 26, 27 may
print four color images on common blanket cylinder 28, which are
transferred to circumferential sections 41, 42, 43, 44, with print unit
20 printing in a manner similar to how print unit 10 prints.

[0021]Surfaces of circumferential sections 31, 32, 33, 34, 41, 42, 43, 44
are raised above surfaces of support cylinders 35, 36, 45, 46 so that
each circumferential section 31, 32, 33, 34, 41, 42, 43, 44 contacts
respective common blanket cylinder 18, 28 and web 12 during a single
revolution about the axis of transfer bodies 135, 136, 145, 146,
respectively. Surfaces of support cylinders 35, 36, 45, 46, which can be
defined as not raised, do not come into contact with web 12 or respective
common blanket cylinders 18, 28. This configuration allows
circumferential sections 31, 32, 33, 34, 41, 42, 43, 44 to accelerate or
decelerate while not in contact with web 12 or respective common blanket
cylinders 18, 28 without smearing the respective four color images on
common blanket cylinders 18, 28 and web 12. In a preferred embodiment,
circumferential sections 31, 32, 33, 34, 41, 42, 43, 44 are driven
independently of one another, allowing each circumferential section 31,
32, 33, 34, 41, 42, 43, 44 to independently accelerate and decelerate.
For example, circumferential section 31 may be driven independently of
circumferential section 32, and therefore circumferential section 32 can
be accelerated while circumferential section 31 is printing an image on
web 12 without causing the image being printed by circumferential section
31 to be smeared.

[0022]Circumferential sections 31, 32, 33, 34, 41, 42, 43, 44 may need to
accelerate, decelerate, or simply travel at constant velocities depending
on the positioning of the transfer bodies 135, 136, 145, 146 in relation
to the respective common blanket cylinders 18, 28, the velocity of web 12
in relation to the velocity of respective common blanket cylinders 18,
28, and the length of the images on the respective first and second
plates of plate cylinders 14, 15, 16, 17, 24, 25, 26, 27.

[0024]In alternative embodiments, plate cylinders 14, 15, 16, 17 each may
include one printing plate including one or more images or printing
plates may not be required, with one or more images directly imaged on
plate cylinders 14, 15, 16, 17. In these embodiments, respective
circumferential sections 31, 32, 41, 42 may receive a first portion of
images from respective common blanket cylinder 18, 28 and print the first
portion of the images on web 12 and respective circumferential sections
33, 34, 43, 44 will receive second portions of the images from common
blanket cylinder 18, 28 and print the second portion of the image on web
12.

[0025]FIGS. 2a to 2c show schematic side views of a nonperfecting printing
press 50 according to an embodiment of the present invention printing on
web 52. FIGS. 2a to 2c show an example of how, according to an embodiment
of the present invention, plate cylinders 54, 55, 56, 57 print four color
images on common blanket cylinder 58, which are transferred to
circumferential sections 61, 62, 63, 64 and printed on web 52, in a
manner similar to how printing units 10, 20 print.

[0026]Each plate cylinder 54, 55, 56, 57 is driven by a respective motor
101, 102, 103, 104. In an alternative embodiment, one or more plate
cylinders 54, 55, 56, 57 can be driven by a common motor. Each plate
cylinder 54, 55, 56, 57 includes a first plate 70, 72, 74, 76,
respectively, and a second plate 71, 73, 75, 77, respectively. Each plate
cylinder 54, 55, 56, 57 is inked with a different colored ink and rotates
clockwise about a respective axis during operation. Plate cylinders 54,
55, 56, 57, during printing mode, are in constant contact, via respective
plates 70, 71, 72, 73, 74, 75, 76, 77 with a common blanket cylinder 58,
which is rotated counterclockwise about an axis by a motor 110. In an
alternative embodiment, a common motor can rotate plate cylinders 54, 55,
56, 57 and common blanket cylinder 58. Surfaces of plates 70, 71, 72, 73,
74, 75, 76, 77 and the surface of common blanket cylinder 58 may travel
at substantially equal velocities.

[0027]Plates 70, 71, 72, 73, 74, 75, 76, 77 of plate cylinders 54, 55, 56,
57 carry formed images 80, 81, 82, 83, 84, 85, 86, 87. Each plate
cylinder 54, 55, 56, 57 is provided with a different colored ink. First
inked images, corresponding to respective formed images 80, 82, 84, 86,
are printed on common blanket cylinder 58 by first plates 70, 72, 74, 76
on plate cylinders 54, 55, 56, 57, respectively. Second inked images,
corresponding to respective formed images 81, 83, 85, 87, are printed on
common blanket cylinder 58 by second plates 71, 73, 75, 77 on plate
cylinders 54, 55, 56, 57, respectively. First inked images are printed on
top of one another on common blanket cylinder 58 to form first four color
images 180, 182, 184, 186, 188, which are shown schematically in FIGS. 2a
to 2c by solid black. Second inked images printed by second plates 71,
73, 75, 77 are printed on top of one another on common blanket cylinder
58 to form first four color images 181, 183, 185, 187, 189, 191, 193,
which are shown schematically in FIGS. 2a to 2c by stripes.

[0031]When plates 70, 71, 72, 73, 74, 75, 76, 77 have portions of
non-print area, there will be corresponding non-printed spaces between
first four color images and second four color images printed on common
blanket cylinder 58 by plates 70, 71, 72, 73, 74, 75, 76, 77. If a length
of a circumference of common blanket 58 is equal to an integer multiple
of the length of the circumference of each plate cylinder 54, 55, 56, 57,
then the non-printed spaces on common blanket cylinder 58 will not vary
with each revolution of blanket cylinder 58. In the schematic embodiment
shown in FIGS. 2a to 2c, the length of the circumference of common
blanket cylinder 58 is assumed to be substantially equal to three times
the surface of each plate cylinder 54, 55, 56, 57. Accordingly, common
blanket cylinder 58 is schematically shown divided into six equal
sections for illustrative purposes. Each section includes an image
transferring portion 102, which has a surface length equal to the length
of each formed image 80, 81, 82, 83, 84, 85, 86, 87, and a non-printed
space 100, which has a surface length equal to the portions of non-print
area on each plate 70, 71, 72, 73, 74, 75, 76, 77. Image transferring
portion 102 and non-printed space 100 demonstrate where inked images of
formed images 80, 81, 82, 83, 84, 85, 86, 87 may be printed on common
blanket cylinder 58 and where portions of non-print area of plates 70,
71, 72, 73, 74, 75, 76, 77 may contact the surface of common blanket
cylinder 58.

[0032]In a preferred embodiment each first four color image forms one
continuous image with an adjacent second four color image. A cutoff
length of each continuous image equals a length of each first four color
image plus the length of each second four color image. To vary the cutoff
of the continuous images printed by printing press 50 the plates 70, 71,
72, 73, 74, 75, 76, 77 could be replaced with respective replacement
plates having images that vary in length from images 80, 81, 82, 83, 84,
85, 86, 87.

[0033]FIG. 3 shows a schematic front view of an embodiment of transfer
body 165 shown in FIGS. 2a to 2c. Transfer body 165 has a support shaft
91, which can attach to a frame or other supporting device to stabilize
support cylinder 65 and circumferential sections 61, 62. In this
embodiment, circumferential sections 61, 62 independently rotate about
support cylinder 65. Circumferential sections 61, 62 are attached to
support arms 94, 95, respectively. Support arms 94, 95 are attached to
respective bearings 92, 93 that are rotatably attached to support shaft
91. Bearings 92, 93 are rotated by respective motors 105, 106 about
support shaft 91, thereby driving circumferential sections 61, 62,
respectively, about support cylinder 65. Transfer body 166 (FIGS. 2a to
2c) and transfer bodies 135, 136, 145, 146 (FIG. 1) may be similarly
configured.

[0034]In alternative embodiments circumferential sections 31, 32, 33, 34,
41, 42, 43, 44, 61, 62, 63, 64 may, respectively, be circumferential
sections on common axes with no respective support cylinders 35, 36, 45,
46, 65, 66. For example, support cylinder 65 would be absent, with
circumferential sections 61 and 62 independently rotating about a common
axis to receive four color images from common blanket cylinder 58 and
print those images on web 52.

[0035]In the preceding specification, the invention has been described
with reference to specific exemplary embodiments and examples thereof. It
will, however, be evident that various modifications and changes may be
made thereto without departing from the broader spirit and scope of
invention as set forth in the claims that follow. The specification and
drawings are accordingly to be regarded in an illustrative manner rather
than a restrictive sense.